1. Field of the Invention
The present invention relates to an image forming apparatus that controls stabilization of an amount of light upon a microscopic light emission in a non-image area, a method of controlling the same, and an image output circuit.
2. Description of the Related Art
In color image forming apparatuses, a so-called white gap phenomenon, in which a white gap that should not be there is formed between images formed adjacently in differing colors, is known. This phenomenon occurs due to an electrostatic latent image, for example an image edge portion, for which a drum surface potential changes sharply, being formed on a photosensitive drum, and a developed image being formed more thinly than it otherwise would be when this portion is developed with a developing apparatus. For example, in an image in which a cyan color band and a black color band are adjacent, the cyan color band and the black color band should be adjacent, but because the developed image of each is respectively formed thinly, a gap between the cyan color and the black color in a final image on a recording material is formed.
It is known that when a microscopic light emission of a light-emitting element of a laser scanner is performed, to an extent that a toner adhesion does not occur, for a non-image area (a non-toner-image-forming-portion) within a full area of a printable region, a thinning of the image is prevented. Hereinafter, performing a microscopic light emission for a non-image area will be referred to as a background exposure, or as a microscopic light emission in a non-image area. In Japanese Patent No. 3684089, a technique for suppressing a situation in which, due to an aerial discharge occurring when transferring a region in which an image does not exist to a transfer medium, an image of another color deteriorates is proposed. In Japanese Patent Laid-Open No. 2003-312050, a technique for reducing unnecessary radiation, occurring when a background exposure is performed, is proposed. In Japanese Patent Laid-Open No. 2012-137743, a technique for stabilizing an amount of light upon a non-image area microscopic light emission is proposed.
However, there are problems in the above described conventional techniques as is described below. For example, in conventional techniques, techniques for reducing unnecessary radiation in a background exposure scheme have been proposed, but these approaches cannot be used for print methods that control a laser directly from a controller unit for generating an image for a printer. In recent years, amongst printer controllers, similarly to personal computers, frequencies that are controlled are being improved in order to improve image processing, network processing, and to improve printer speeds.
For this reason, in the personal computers and printer controllers, in recent years, in order to solve unnecessary radiation problems, a technology known as SSCG has come to be employed commonly. An SSCG (Spread Spectrum Clock Generator) is a semiconductor technology employed as a counter-measure to emitted electromagnetic noise (unnecessary radiation) of an electronic device.
Generally, an electronic device including a color image forming apparatus cannot be put on the market if it does not clear a regulation pertaining to unnecessary radiation. In the Japanese VCCI standard, there are categories of CLASS A and CLASS B, and because CLASS B is for products for which there is a possibility of installation in a family home, it is stricter as a standard, and for example, it is necessary to meet this standard for SFPs. With such unnecessary radiation regulations, tolerances are laid down for each frequency, and the standard is not satisfied if these tolerances are exceeded even by a small amount. An SSCG is an unnecessary radiation counter-measure technology that takes advantage of a characteristic of unnecessary radiation for a target peak value. More specifically, a peak value of unnecessary radiation due to a clock signal, or of unnecessary radiation due to a switching frequency of a device that operates with that clock signal as a basis, can be suppressed. However, because frequency is caused to fluctuate, the total energy quantity of the unnecessary radiation does not change.
However, in a color image forming apparatus, SSCG technology cannot be used for a clock of a circuit for outputting an image directly from a controller to a laser. This is because an output image is distorted since a modulation subtly occurs on a width of the image with respect to a defined width, and it is common to use a clock that does not use an SSCG for an image output signal of an image forming apparatus that performs direct laser control. In this way, there is the problem that, because an SSCG clock cannot be used when performing a background exposure, unnecessary radiation problems cannot be solved, and so devices cannot be put onto the market.